flesh out how we use gateway-conformance for testing subdomain and path modes

[SgtPooki]

@lidel @achingbrain

I'm going to be moving gateway conformance tests code into @helia/verified-fetch.

That will likely require:

1. setting up a basic gateway host (I'm imagining a basic nodejs http server that passes requests directly to verified-fetch)
2. setting up subdomain gateway for testing environment (i.e. porting over reverse-proxy.js from this repo)
3. setting up gateway conformance fixture loading in helia-verified-fetch repo (pulling logic from helia-http-gateway and service-worker-gateway repos)

Once that is done, we should be able to get away with just CI tests in helia-http-gateway and service-worker-gateway.

Are you two okay with this plan?

[lidel]

Sgtm. Focus on verified-fetch, where nearly all of relevant code related to web pathing and ipfs:// behaviors will live.

[SgtPooki]

I am going to call this closed since this issue is basically tracking agreement on how to proceed. #224 tracks completion of the work.